CR Proposal (#283)

### Issues resolved by this PR: 

- Clear split between requirements for rule authors vs. rule implementers : Closes #272
- Need a definition of Test Target : Closes #271
- 16. Rule Aggregation - Add Requirement : Closes #252
- Accessibility Requirements: Updates requested (Shadi) : Closes #250
- 15.2. Accuracy Benchmarking - Update definition : Closes #236
- Outcomes of atomic tests : Closes #235
- clarifying the relationship between rule application and accessibility conformance : Closes #227
- ACT i18n checks : Closes #226
- Clarify the definition of Rule Aggregation : Closes #165
- Clarify how to do "Implementation validation" and "accuracy benchmarking" for manual or semi-automated rules : Closes #163
- Clarify the output format definition : Closes #162
- Mark all Informative sections as such : Closes #280
- "Failed" / "Passed" or "Fail"/"Pass"? : Closes #279
- Require Rule ID's in Atomic Rule List : Closes #261
- Scope sections states ACT rules should not be used for conformance : Closes #281
- Section “13. Accessibility Support” unclear : Closes #221
- Examples need to be identified accessibly : Closes #187

### Outstanding discussions before CR: 

- List of features for exit criteria #224

### Outstanding editorials before CR:

- Need non-versioned biblio reference tags #216


<!--
    This comment and the below content is programatically generated.
    You may add a comma-separated list of anchors you'd like a
    direct link to below (e.g. #idl-serializers, #idl-sequence):

    Don't remove this comment or modify anything below this line.
    If you don't want a preview generated for this pull request,
    just replace the whole of this comment's content by "no preview"
    and remove what's below.
-->
***
<a href="https://pr-preview.s3.amazonaws.com/w3c/wcag-act/pull/283.html" title="Last updated on Oct 12, 2018, 12:04 PM GMT (1776294)">Preview</a> | <a href="https://pr-preview.s3.amazonaws.com/w3c/wcag-act/283/38370ea...1776294.html" title="Last updated on Oct 12, 2018, 12:04 PM GMT (1776294)">Diff</a>